Abstract
In the study, ultrasonic longitudinal mode guided waves were employed to detect defects in elbowed tubes (without welds) with a diameter of 10 mm. Finite element simulation results highlighted that the emitted L(0,1) mode guided waves experienced strong reflection and mode conversion at the elbow region to generate F(1,1) mode, followed by slow and weak F(2,1) mode. The guided wave reflected from the elbow with a through-wall defect was manifested as two overlapped wave packets, which were good indicators of a defective elbow. To conduct L(0,1) mode guided waves inspection on the small-diameter elbowed tubes, a novel tailored squirrel-cage magnetostrictive sensor was employed in the experiment. The new sensor employed the configuration of segmental iron-cobalt strips and small-size permanent magnet arrays. The entire sensor is composed of two identical C-shaped sensor elements and can be recycled and installed conveniently. Experimental results obtained from healthy and defective tubes were consistent with the conclusions obtained from finite element simulations. An artificial through-wall defect at the elbow and a notch defect at the straight part of the tube could be simultaneously detected by L(0,1) mode guided waves through comparing experimental signals with simulation results.
Highlights
Metallic elbowed tubes with a small diameter are crucial parts for transporting waste heat, fuel oil, water coolant, etc., among power equipment of ships [1]
The experimental results were consistent with the conclusions obtained from finite element simulation results, indicating that the through-wall defect at the elbow and a notch defect at the straight part could be simultaneously detected by L(0,1) mode Ultrasonic guided waves (UGWs)
Both finite element simulations and experiments were performed to investigate the ability of L(0,1) mode guided waves in detecting the defect of steel tubes (10 mm in diameter, 2 mm in wall thickness) with 90° elbow
Summary
Metallic elbowed tubes with a small diameter (less than 20 mm) are crucial parts for transporting waste heat, fuel oil, water coolant, etc., among power equipment of ships [1]. Ultrasonic guided waves (UGWs) technology is another candidate option for defect inspection in small-diameter elbowed metallic tubes. A novel squirrel-cage magnetostrictive sensor (MsS) was tailor-made for smalldiameter tubes to generate and receive L(0,1) mode UGWs. The performances of the novel squirrel-cage MsS in detecting. Journal of Sensors artificial defects in small-diameter elbowed tubes were experimentally explored. The experimental results were consistent with the conclusions obtained from finite element simulation results, indicating that the through-wall defect at the elbow and a notch defect at the straight part could be simultaneously detected by L(0,1) mode UGWs. In Section 2, finite element simulations were performed to investigate the propagation behavior of UGWs in smalldiameter elbowed tubes.
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